In general, an ESC system stably maintains an attitude of a vehicle in an emergency situation by sensing wheel velocity, yaw moment, a steering angle, pressure of accelerator/brake pedal, and the like of the vehicle to optimally control braking power of each wheel.
When vehicle speed and lateral acceleration during driving satisfy reference conditions (e.g., vehicle speed of 40 KPH or more, lateral acceleration 0.6 g or more), the ESC system requests an engine control unit (ECU) to increase or decrease engine torque in order to secure driving stability of the vehicle.
Meanwhile, a traction control system (TCS) prevents driving wheels from being spun when the vehicle starts, accelerates, or climbs on a slippery road, thereby allowing the vehicle to be stably maintained on an X axis (an axis in a lengthwise direction) line.
The TCS also maintains cornering stability, and requests the engine control unit (ECU) to increase or decrease the engine torque in order to prevent the wheels of a driving shaft of the vehicle from being spun aside, which causes a track departure.
If the ECU receives a continuous torque decrease request from the ESC system or the TCS, the ECU rapidly performs a torque control by considering that the continuous torque decrease request of the ESC system is directly linked with stability of the vehicle. That is, the ECU retards an ignition timing or cut fuel by rapidly performing torque control, so as to decrease the engine torque.
The retardation of the ignition timing described above increases temperature of exhaust gas to thereby excessively increase temperature of catalyst, and the cut of the fuel causes air and the catalyst to be directly in contact with each other to thereby excessively increase the temperature of the catalyst, which cause dissolution of the catalyst (damage of the catalyst).
Since an apparatus for controlling an engine according to the related art decreases the engine torque by simply retarding the ignition timing or cutting the fuel upon receiving the torque decrease request from the ESC system or the TCS, there is a problem that the damage of the catalyst performing a function purifying the exhaust gas of the vehicle is caused.